(a) Field of the Invention
The present invention relates to a switch controller and a converter having the same. In further detail, it relates to a switch controller that can compensate efficiency deterioration according to an input voltage of a converter, and a converter having the same.
(b) Description of the Related Art
In general, when forming a power factor controller (PFC) circuit with a converter, a method (hereinafter referred to as a multi-input method) that controls a level of an output voltage to be changed according to an input voltage is advantageous in efficiency of the converter compared to a method that maintains an output voltage in a constant level. A slope at which an input current is decreased when a switch of the converter is turned off is proportional to a difference between the output voltage and the input voltage. When the input voltage is decreased so that the output voltage is decreased, the difference between the output voltage and the input voltage is decreased compared to the case in which the output voltage is maintained at a constant level. Then, the input current decreasing slope is decreased and thus a switching operation period of the switch is increased so that a switching loss is decreased. In addition, since the output voltage is decreased, a duty of the switch is decreased so that a conduction loss is also decreased. Accordingly, efficiency of a converter using the multi-output method is increased.
In general, the converter generates a reference voltage to determine a duty of a switch that controls operation of the converter. The converter using the multi-output method senses an input voltage and generates a reference voltage according to the input voltage, or senses an output voltage and generates a reference voltage according to an input voltage. As described, the converter using the multi-output method requires an additional configuration for sensing an input voltage or an output voltage to generate a reference voltage.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.